There was a Radiant Systems P1510 left over in an abandoned restaurant I bought a while back. It I couldn't find a power cord so I just used one from an old computer monitor. When I turn the P1510 on the fans start spinning but the screen doesn't do anything, it doesn't even light up a tiny bit. I plugged an ethernet cord into it while it was on and then plugged it into my mac and it showed that I was giving it a secure internet connection. Does anyone know what is wrong? Do I need the actual power cord?